Luminaire



April 1, 1947. w, RQLPH 2,418,195

LUMINAIRE Filed Nqv. 2, 1944 INVENIFR THOMAS W- 0L PH ATTORNEY Patented Apr. .1, 1947 LUMINAIRE Thomas W. Rolph, Newark, Ohio, assignor'to Holophane Company, Inc., New York, N. Y., a corporation of Delaware Application November 2, 1944, Serial No. 561,511 4 Claims. (Cl. 240-103) The present invention relates to luminaires, and is more particularly directed toward luminaires employing elongated light sources such as fluorescent lamps and having reflecting troughs to direct the light downwardly.

For optimum distribution of reflected light the reflector has heretofore been made of specular re fleeting sheet metal with a smooth contour and quite generally provided with a cusp back of the lamp so as to deliver the reflected light in directions to miss the opaque lamp.

The present invention contemplates a luminaire having a lamp and reflector with substantially the same efiective redistribution of light tor is directed downwardly and across the axis of the luminaire.

In Figure 2 the light sourceis again indicated at In and the reflecting trough is composed of an upper flat member l3 and two flat side members l4, l4. These, as above mentioned, are typically pieces of pressed glass. The upper piece has a series of prism-like elements il3tl, l3b, I30, I3d, l3e, l3 l3g, l3h, l3i, I39, with surfaces tipped to the horizontal plane of the lower surface. The upper part of the side member I has similar prism-like ribbings Ha, I 4b, Mc, I4d,,|4e, Mf, Mg, whose upper surfaces are tipped to the plane of the inner or lower surface. The entire as is accomplished by a specular metal reflector, outer or upper surface of the reflector is mirsuch, for example, as the one just referred to, rored, as indicated by the letter M. and wherein the new reflector is made of flat or The light rays from the 70 to 170 angles above nearly flat elements of transparent material the nadir are redrawn the same as in Figure l, ribbed either internally or externally and mirand it will be noted that these light rays enter rored to control the redirection of the light. the transparent medium, i. e., the glass of the These reflectors are typically mirrored glass reflectors, pass to the outer reflecting surface which may be pressed flat or nearly flat and asand are reflected back into the glass and transsembled in the desired position. mitted into the air at angles which differ from The accompanying drawings show, for purwhat the angles would have been had there been poses of illustrating the present invention, two no tipping of the reflecting surfaces. This reembodiments in which the invention may take form, it being understood that the drawings are illustrative of the invention rather than limiting the same.

In these drawings:

Figure 1 illustrates a typical form of specular reflector with fluorescent lamp showing a typical contour and light redirection by such reflector;

Figures 2 and 3 are cross sectional views through luminaires with the mirrored reflectors, the ribs being external; and

Figure 4 is a fragmentary view of an internally ribbed mirrored reflector.

In Figure 1 the light source It! is illustrated in the form of a single tubular lamp, but, of course, two or more lamps may be employed as customary. A conventional reflector form is illustrated at II, this form being considered as a corresponding form for the reflectors illustrated in Figures 2 and 3 which are substantially the optical equivalent.

In Figure'l light rays have'been drawn from the center of the light source at every 10 from 70 to 170 above the nadir and the corresponding specularly reflected light rays indicated at II. It will be apparent that such a reflector directs all the reflected light out through its mouth, the light from the upper part of the reflector being directed away from the nadir to miss the lamp, while the light from the lower part of the reflecflection takes place, as indicated in the drawing by the lines I5 terminating inarrows, and it will be seen that the action is substantially the same as that produced by the smooth, specular reflector of Figure 1; that is to say, the light emitted in the region of zenith is reflected downwardly and away from the nadir so as to escape between the lamp and the outer part of the reflector, while the light which strikes the side members l4, I4 is reflected downwardly and toward the fixture axis in the same way as the corresponding direct light was reflected by the reflector of Figure 1.

In Figure 2 the lower part of the side pieces l4, It has the same contour and position as the lower part of the reflectorll of Figure 1, and hence this reflector need have no external prismlike ribs. For purposes of comparison the portion of the curved reflector ll intercepting the same zone of direct light rays as the ribbed mirrored reflector is indicated in dotted lines, and the reference character II is applied. If the mirrored reflector were smooth and followed the same contour as the metal specular reflector, the redistribution of the light would be the same as in Figure 1. Manufacturing limitations make it impossible to economically make such curved reflector forms of the size required. The same optical effect is obtained according to the present invention by tipping the reflecting faces of the 3 prism-like ribs so as to bring them to approximately the same slope as the opposed portion of curve ll. These tipped surfaces do not come into exactly the same slope, because of the deviations in light reflection caused by the refraction on entering and on leaving the transparent medium. This relocation of the reflecting surface in steps out of parallelism with the incident surface makes it possible to have the equivalent of a flat reflector with thin sections.

In the form shown in Figure 3 the reflector comprises two flat sloping plates 20. The portions of these plates falling inside the curve II have regressed prism-like ribbings 2| mirrored, as shown, and these redirect the light rays, as shown at 23, in practically the same way as the part of the specular surface If occupying the It is also possible to have the regressed prisms in the incident surface as indicated at 24 in Figure 4. The reflected ray 25 has a different path than it would have had but for the ribbing.

Since it is obvious that the invention may be embodied in other forms and constructions within the scope of the claims, I wish it to be understood that the particular forms shown are but a few of these forms, and various modifications and changes being possible, I do not otherwise limit myself in any way with respect thereto.

What is claimed is:

1. The combination with a horizontal rectilinear fluorescent lamp of an inverted troughshaped reflector about said lamp for obtaining from thelamp substantially the same distribution of reflected light originating in the lamp as that obtained from an inverted trough-shaped specular reference reflector parallel with the lamp and occupyinga predetermined position in space and having a smooth profile which includes downwardly and outwardly diverging sides and a cusped inwardly concave upper portion shaped to reflect high angle direct light downwardly and outwardly past the lamp, comprising flat transparent plates of generally uniform thickness parallel with the source, disposed to form an inverted trough and occupying a different position in space than the reference reflector but intercepting the same zone of direct light, the plates being externally mirrored to interiorly reflect light incident on their outer surfaces at angle less than the critical angle, one surface of each plate being smooth, the other having over at least a portion thereof, relatively narrow side by side rib forming areas tilted to the smooth surface in variant amounts such that the angles 'of refraction of entering rays differ from the angles of incidence of corresponding reflected rays on the emitting surface to such an extent that the emitted rays are Substantially parallel to the corresponding reflected rays which the smooth profile reference reflector would have produced.

2. The combination with a horizontal-fluorescent lamp of a trough-shaped reflector symmetrical about a vertical plane through the source, the reflector being composed of flat externally mirrored glass plates each having a smooth surface and an opposed surface comprising at least in part a series of adjacent tilted areas regressed to a plane parallel with the smooth surface, the angle of tilt of the areas varying from area to area such that the over all deviation accomplished by refraction at the incident surface followed by reflection at the mirrored surface and refraction at the emergent surface is substantially equal to the deviation obtainable by specular reflection of corresponding direct rays by a trough-shaped reflector of a smooth profile occupying a different position in space and having straight sidesand a cusped inwardly concave top.

3. The combination with a rectilinear horizontal fluorescent lamp of an inverted troughshaped reflector about the lamp and comprising a horizontal flat plate and two downwardly and outwardly sloping side plates, the plates being transparent and externally mirrored and having one surface smooth, the horizontal plate having at each side of the vertical plane through the lamp a series of prismatic ribs parallel with the lamp and of variant angle of tilt to the smooth surface to reflect light downwardly andoutwardly to pass down laterally of the lamp, the upper portions of th side plates having a series of prismatic ribs of variant angle of tilt to the smooth surface and less steep than the smooth surface to reflect light downwardly and inwardly to cross said vertical plane.

4. The combination with a rectilinear-horizontal fluorescent lamp of an inverted troughshaped reflector about the lamp and comprising two flat plates sloping at the same angle to the vertical and meeting above the lamp center, the plates being externally mirrored, one side of each plate being smooth, the other side having adjacent tilted areas regressed to a plane parallel to the smooth surface, the areas below a region substantially level with the lamp center being steeper than the smooth surface and emitting light generally downward, the areas immediately above this region being less steep than the smooth surface and emitting light generally downward laterally of the lamp, the areas adjacent the vertex of the plates being steeper than the smooth surface and reflecting high angle vertical light onto the other plate.

THOMAS W. ROLPH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,096,453 Exelmans Oct. 19, 1937 2,330,924 Rolph Oct. 5, 1943 2,346,717 Ainsworth Apr. 18, 1944 1,976,163 Exelmans Oct. 9, 1934 

